Various systems use transponders to identify objects from a distance by associating a transponder with the object. The transponders, also known as radio frequency identification (RFID) tags, are typically programmed with unique identification codes that identify the object. FIG. 7 illustrates a conventional tag and reader system. A reader 710 may include an inductive element 712 generating a magnetic field that energizes a tag 720. The tag 720 may include an inductive element 722 and a load 724. When the tag 720 is in proximity of the reader 710, the magnetic field generated by the reader 710 energizes the tag 720 by inducing a voltage across the inductive element 722.
The tag 720 may transmit limited information back to the reader 710, such as an identification code. For example, the load 724 shunted across the inductive element 722 when the tag 720 is energized causes the magnetic coupling between the reader 710 and the tag 720 to change. The change in the magnetic coupling results in voltage fluctuations across the inductive element 712 of the reader 710, which when demodulated identifies the information exchanged between the tag 720 and the reader 710.
Readers and tags, such as shown in FIG. 7, are used for a number of applications. However, these applications are usually limited to remote identification applications. Furthermore, in these applications only limited information (e.g., identification number) is typically transmitted from the tag.